Solar cell and photovoltaic module

ABSTRACT

A solar cell and a photovoltaic module are disclosed, including: a substrate; a tunneling dielectric layer and a doped conductive layer disposed on the substrate, the tunneling dielectric layer being disposed between the doped conductive layer and a surface of the substrate, the doped conductive layer having a N-type or P-type doping element and having a plurality of first heavily doped regions spaced apart from each other and extending in a first direction, a doping concentration in the first heavily doped regions being greater than that in other regions of the doped conductive layer; a passivation layer disposed on a surface of the doped conductive layer facing away from the substrate; and a plurality of electrodes spaced apart from each other, extending in a second direction and penetrating the passivation layer to contact the doped conductive layer, at least two first heavily doped regions contacting a same electrode.

CROSS-REFERENCE TO RELATED APPLICATION

The application claims priority to Chinese Patent Application No.202111501018.6, filed on Dec. 9, 2021, the content of which isincorporated herein by reference in its entirety.

TECHNICAL FIELD

Embodiments of the present disclosure relate to the field of solar cell,in particular to a solar cell and a photovoltaic module.

BACKGROUND

The performance of a solar cell (for example, photoelectric conversionefficiency) is subject to optical and electrical losses. The opticalloss may be resulted from, for example, reflection of a front surface ofthe cell, shadows of grid lines, non-absorption of a long-wave band, andthe like. The electrical loss may be resulted from, for example,photogenerated carrier recombination on a surface of a semiconductor andinside the semiconductor, contact resistance between the semiconductorand metal grid lines, contact resistance between a metal and thesemiconductor, and the like.

In order to reduce the electrical loss of the solar cell, a tunnelingoxide structure for passivating metal contacts may be formed on asurface of the cell. The tunneling oxide structure includes anultra-thin tunneling dielectric layer and a doped conductive layer. Thestructure can provide good surface passivation, thereby reducingcomposite current caused by metal contact and increasing theopen-circuit voltage and short-circuit current of the cell. Though thetunneling oxide structure can optimize the performance of the solarcell, there are still many factors affecting the performance of thesolar cell of this type. Thus, it is of great significance to developsolar cells highly efficient in passivating contacts.

SUMMARY

Embodiments of the present disclosure provide a solar cell and aphotovoltaic module, which are conducive to improving photoelectricconversion efficiency of a solar cell with passivating contacts.

In an aspect, embodiments of the present disclosure provide a solar cellincluding a substrate, a tunneling dielectric layer, a doped conductivelayer, a passivation layer, and a plurality of electrodes. The tunnelingdielectric layer and the doped conductive layer disposed on thesubstrate. The tunneling dielectric layer is disposed between the dopedconductive layer and a surface of the substrate. The doped conductivelayer has a doping element of an N type or a P type. The dopedconductive layer has a plurality of first heavily doped regions spacedapart from each other and extending in a first direction. A dopingconcentration in the plurality of first heavily doped regions is greaterthan a doping concentration in other regions of the doped conductivelayer. The passivation layer disposed on a surface of the dopedconductive layer facing away from the substrate. The plurality ofelectrodes spaced apart from each other and extending in a seconddirection. The plurality of electrodes penetrate the passivation layerto contact the doped conductive layer, and at least two of the pluralityof first heavily doped regions are in contact with a same electrode.

In an embodiment, the plurality of first heavily doped regions have adepth in a direction perpendicular to the surface of the substrate thatis smaller than or equal to a thickness of the doped conductive layer ina direction perpendicular to the surface of the substrate.

In an embodiment, a ratio of the depth of the plurality of first heavilydoped regions to the thickness of the doped conductive layer is in arange of 80% to 100%.

In an embodiment, the thickness of the doped conductive layer is in arange of 40 nm to 150 nm.

In an embodiment, the substrate has a plurality of second heavily dopedregions. A doping concentration in the plurality of second heavily dopedregions is greater than a doping concentration in other regions of thesubstrate. Each of the plurality of second heavily doped regions isaligned with a respective one of the plurality of first heavily dopedregions. The plurality of first heavily doped regions and the pluralityof second heavily doped regions have doping elements of a same type.

In an embodiment, the doping concentration in the plurality of secondheavily doped regions is less than or equal to the doping concentrationin the plurality of first heavily doped regions.

In an embodiment, the doping concentration of the plurality of firstheavily doped regions is in a range of 2E+20 cm⁻³ to 1E+22 cm⁻³.

In an embodiment, the plurality of second heavily doped regions have adepth in a range of 0.001 μm to 1 μm in a direction perpendicular to thesurface of the substrate.

In an embodiment, the tunneling dielectric layer has a plurality ofthird heavily doped regions extending through the tunneling dielectriclayer along a thickness direction thereof to contact the plurality offirst heavily doped regions and the plurality of second heavily dopedregions, respectively. Each of the plurality of third heavily dopedregions is aligned with a respective one of the plurality of firstheavily doped regions. The plurality of first heavily doped regions andthe plurality of third heavily doped regions have doping elements of asame type.

In an embodiment, in a direction along which the plurality of firstheavily doped regions are distributed, each of the plurality of firstheavily doped regions has a width smaller than a width of a respectiveone of the plurality of second heavily doped regions, and smaller thanor equal to a width of a respective one of the plurality of thirdheavily doped regions.

In an embodiment, a ratio of a sum of surface areas of the plurality offirst heavily doped regions to a surface area of the doped conductivelayer is in a range of 1% to 20%.

In an embodiment, each of the plurality of first heavily doped regionshas a width in a range of 20 μm to 100 μm in a direction along which theplurality of first heavily doped regions are distributed.

In an embodiment, the plurality of first heavily doped regions arespaced apart from each other with a distance in a range of 0.8 mm to 4mm in a direction along which the plurality of first heavily dopedregions are distributed.

In an embodiment, the doped conductive layer includes at least one of apolysilicon layer, an amorphous silicon layer and a microcrystallinesilicon layer.

In an embodiment, the substrate has a first surface and a second surfaceopposing to each other. The tunneling dielectric layer and the dopedconductive layer are disposed on at least one of the first surface andthe second surface of the substrate.

In an embodiment, the substrate and the doped conductive layer havedoping elements of a same type.

In another aspect, embodiments of the present disclosure provide aphotovoltaic module including a cell string, a package adhesive film anda cover plate. The cell string includes a plurality of solar cells. Thepackage adhesive film is configured to cover a surface of the cellstring. The cover plate is configured to cover a surface of the packageadhesive film facing away from the cell string. The solar cell includesa substrate, a tunneling dielectric layer, a doped conductive layer, apassivation layer, and a plurality of electrodes. The tunnelingdielectric layer and the doped conductive layer disposed on thesubstrate. The tunneling dielectric layer is disposed between the dopedconductive layer and a surface of the substrate. The doped conductivelayer has a doping element of an N type or a P type. The dopedconductive layer has a plurality of first heavily doped regions spacedapart from each other and extending in a first direction. A dopingconcentration in the plurality of first heavily doped regions is greaterthan a doping concentration in other regions of the doped conductivelayer. The passivation layer disposed on a surface of the dopedconductive layer facing away from the substrate. The plurality ofelectrodes spaced apart from each other and extending in a seconddirection. The plurality of electrodes penetrate the passivation layerto contact the doped conductive layer, and at least two of the pluralityof first heavily doped regions are in contact with a same electrode.

BRIEF DESCRIPTION OF THE DRAWINGS

One or more embodiments are described as examples with reference to thecorresponding figures in the accompanying drawings, and the examples donot constitute a limitation to the embodiments. The figures in theaccompanying drawings do not constitute a proportion limitation unlessotherwise stated.

FIG. 1 is a schematic structural diagram of a solar cell according to anembodiment of the present disclosure.

FIG. 2 is a schematic diagram of a local structure of a solar cellaccording to an embodiment of the present disclosure.

FIG. 3 is a schematic diagram of another local structure of a solar cellaccording to an embodiment of the present disclosure.

FIGS. 4 a and 4B are ECV doping graphs of a solar cell according to anembodiment of the present disclosure.

FIG. 5 is a schematic structural diagram of a solar cell according toanother embodiment of the present disclosure.

FIG. 6 is a schematic structural diagram of a solar cell according tostill another embodiment of the present disclosure.

FIG. 7 is a schematic structural diagram of a solar cell according tostill another embodiment of the present disclosure.

FIGS. 8 to 16 are schematic structural diagrams corresponding to varioussteps of a method for manufacturing a solar cell according to anembodiment of the present disclosure.

DETAILED DESCRIPTION

As discussed in the background, the photoelectric conversion efficiencyof the solar cell with passivating contacts needs to be furtherimproved.

For this purpose, embodiments of the present disclosure provide a solarcell, a method for preparing the solar cell, and a photovoltaic module.In the solar cell, a doped conductive layer has a plurality of firstheavily doped regions spaced apart from each other and extending in afirst direction, a doping concentration in the plurality of firstheavily doped regions is greater than a doping concentration in otherregions of the doped conductive layer except the plurality of firstheavily doped regions, and at least two of the plurality of firstheavily doped regions are in contact with a same electrode. In this way,the doping concentration in the doped conductive layer can improvecapability of current transmission, reduce sheet resistance of the dopedconductive layer, reduce an open-circuit voltage, and improvephotoelectric conversion efficiency. Since the doping concentration inthe first heavily doped regions is greater than the doping concentrationin the other regions of the doped conductive layer and at least two ofthe first heavily doped regions are in contact with the same electrode,a good ohmic contact is formed between the first heavily doped regionsand the electrodes, thereby reducing a contact resistance between thedoped conductive layer and the electrodes and improving thephotoelectric conversion efficiency of the solar cell. Meanwhile, theelectrodes can be spaced farther from each other to save material forthe electrodes, thereby reducing production cost, increasing a lightreceiving area of a surface of the solar cell, and improving thephotoelectric conversion efficiency.

The embodiments of the present disclosure will be described in detailbelow with reference to the accompanying drawings in order to make theobjectives, technical solutions and advantages of the present disclosureclearer. However, those skilled in the art may appreciate that, in thevarious embodiments of the present disclosure, numerous technicaldetails are set forth in order to provide the reader with a betterunderstanding of the present disclosure. However, the technicalsolutions claimed in the present disclosure may be implemented withoutthese technical details and various changes and modifications based onthe following embodiments.

Referring to FIGS. 1 to 4 , FIG. 1 is a schematic structural diagram ofa solar cell according to an embodiment of the present disclosure. FIG.2 is a schematic diagram of a local structure of a solar cell accordingto an embodiment of the present disclosure. FIG. 3 is a schematicdiagram of another local structure of a solar cell according to anembodiment of the present disclosure. FIGS. 4 a and 4B are ECV dopinggraphs of a solar cell according to an embodiment of the presentdisclosure.

In an aspect, the embodiments of the present disclosure provide a solarcell, as shown in FIG. 2 , including a substrate 100, a tunnelingdielectric layer 140, a doped conductive layer 150, a passivation layer160, and a plurality of electrodes 170. The tunneling dielectric layer140 and the doped conductive layer 150 disposed on the substrate 100.The tunneling dielectric layer 140 is disposed between the dopedconductive layer 150 and a surface of the substrate 100. The dopedconductive layer 150 has a doping element of an N type or a P type. Thedoped conductive layer 150 has a plurality of first heavily dopedregions 151 spaced apart from each other and extending in a firstdirection. A doping concentration in the plurality of first heavilydoped regions 151 is greater than a doping concentration in otherregions of the doped conductive layer 150 except the plurality of firstheavily doped regions 151. The passivation layer 160 disposed on asurface of the doped conductive layer 150 facing away from the substrate100. The plurality of electrodes 170 spaced apart from each other andextending in a second direction. The plurality of electrodes 170 eachpenetrates the passivation layer 160 to contact the doped conductivelayer 150, and at least two of the plurality of first heavily dopedregions are in contact with a same electrode 170.

In some embodiments, the solar cell is a Tunnel Oxide Passivated Contact(TOPCon) cell, which may be a double-sided TOPCon cell or a single-sidedTOPCon cell.

The substrate 100 is configured to absorb incident photons to producephotogenerated carriers. In some embodiments, the substrate 100 is asilicon substrate 100, which may include at least one of single crystalsilicon, polysilicon, amorphous silicon and microcrystalline silicon. Inother embodiments, the substrate 100 may include materials such assilicon carbide, organic materials, or multinary compounds. Themultinary compounds may include, but are not limited to, materials suchas perovskite, gallium arsenide, cadmium telluride, copper indiumselenium, and the like. For example, substrate 100 in the presentdisclosure is a single crystal silicon substrate.

In some embodiments, the substrate 100 has a first surface 101 and asecond surface 102 opposing to each other. In this case, the firstsurface 101 of the substrate 100 is referred to as a front surface andthe second surface 102 of the substrate 100 is referred to as a rearsurface. Further, for a single-sided cell, the first surface 101 of thesubstrate 100 is a light receiving surface, and the second surface 102of the substrate 100 is a back surface; for a double-sided cell, boththe first surface 101 and the second surface 102 may serve as lightreceiving surfaces to absorb incident light.

In some embodiments, the substrate 100 has a doping element of an N typeor a P type. The N-type element may be a V group element such as aphosphorus (P) element, a bismuth (Bi) element, an antimony (Sb) elementor an arsenic (As) element. The P-type element may be a III groupelement such as a boron (B) element, an aluminum (Al) element, a gallium(Ga) element or an indium (In) element. For example, when being a P-typesubstrate, the substrate 100 has the doping element of the P type. Foranother example, when being an N-type substrate, the substrate 100 hasthe doping element of the N type.

In some embodiments, the substrate 100 and the doped conductive layer150 have doping elements of a same type. For example, the doping elementin the substrate 100 is of the N type, and the doping element in thedoped conductive layer 150 is of the N type.

In some embodiments, the solar cell includes an emitter 110 disposed onthe first surface 101 of the substrate 100. The substrate 100 forms a PNjunction with the emitter 110, for example, an N-type doping element inthe substrate 100 and a P-type doping element in the emitter 110. Inother embodiments, the emitter 110 may be regarded as a part of, or inother words, an extension of, the substrate 100. Further, a surface ofthe emitter 110 may be a pyramid-textured surface to reduce lightreflection on the surface of the emitter 110, increase light absorptionand utilization, and improve conversion efficiency of the solar cell.

In some embodiments, the tunneling dielectric layer 140 and the dopedconductive layer 150 are disposed on the second surface 102 of thesubstrate 100. The tunneling dielectric layer 140 reduces a density ofan interface state between the substrate 100 and the doped conductivelayer 150 by chemical passivation, reduces minority carriers and holerecombination, and thus is advantageous for reduction of a Jo loadcurrent. The tunneling dielectric layer 140 can be configured to tunnelminority carriers into the doped conductive layer 150, and then theminority carriers are transversally transmitted in the doped conductivelayer 150 and collected by the electrodes 170, thereby greatly reducinga recombination current caused by contact between the electrode 170 andthe doped conductive layer 150, and increasing an open-circuit voltageand a short-circuit current of the solar cell.

In some embodiments, the tunneling dielectric layer 140 may include, butis not limited to, a dielectric material with a tunneling effect, suchas silicon oxide, silicon nitride, silicon oxynitride, intrinsicamorphous silicon, and intrinsic polysilicon. The tunneling dielectriclayer 140 may have a thickness in a range of 0.5 nm to 2 nm,particularly 0.5 nm to 1.5 nm, and further particularly 0.5 nm to 1.2nm.

The doping concentration and doping depth of the doped conductive layer150 affect the photoelectric conversion efficiency of the solar cell.The doping concentration and doping depth of the doped conductive layer150 are in appropriate ranges to ensure good ohmic contact between thedoped conductive layer 150 and the electrode 170 for effectivetransmission of the minority carriers, that is, a high conversionefficiency of solar cell, and meanwhile to ensure lower composite lossof the surface of the substrate 100 and good interface passivationeffect of the tunneling dielectric layer 140 to improve the conversionefficiency of the solar cell.

Methods for detecting impurity concentration distribution may include aspread resistance method, a capacitance-voltage (C-V) method, asecondary ion mass spectrometry (SIMS) method, a differential Hallmethod, an electrochemical capacitance-voltage (ECV) method, and thelike. In some embodiments, the electrochemical capacitance-voltagemethod is employed for detecting the ranges of the doping concentrationand doping depth of the doped conductive layer 150. Referring to FIG. 4, the relationship between the doping concentration and the doping depthof the doped conductive layer 150 in the solar cell of the presentdisclosure conforms to curves shown in the ECV doping graph of FIG. 4 .The curves include a curve for the first heavily doped regions 151 and acurve for the other regions of the doped conductive layer 150. Thespecific doping concentration and the specific doping depth of the dopedconductive layer 150 are not limited herein, as long as the curves shownin FIG. 4 are satisfied.

The doped conductive layer 150 may include at least one of apolycrystalline semiconductor, an amorphous semiconductor and amicrocrystalline semiconductor, and particularly, the doped conductivelayer includes at least one of a polysilicon layer, an amorphous siliconlayer or a microcrystalline silicon layer. The doped conductive layer150 has a thickness in a range of 40 nm to 150 nm, particularly, 60 nmto 90 nm, which can ensure lower optical loss of the doped conductivelayer 150 and good interface passivation effect of the tunnelingdielectric layer 140, thereby improving efficiency of the cell. Forexample, in the present disclosure, the material of the doped conductivelayer 150 is polysilicon, and the thickness of the doped conductivelayer 150 is 80 nm.

The relationship between the doping concentration and the doping depthof the first heavily doped regions 151 of the doped conductive layer 150conforms to the curve for the first heavily doped regions 151 as shownin FIG. 4 . The specific doping concentration and the specific dopingdepth of the first heavily doped regions 151 are not limited herein, aslong as the curve shown in FIG. 4 is satisfied. Similarly, therelationship between the doping concentration and the doping depth ofthe other regions of the doped conductive layer 150 conforms to thecurve for the other regions.

Further referring to FIGS. 1 to 3 , in some embodiments, a ratio of asum of surface areas of the plurality of first heavily doped regions 151to a surface area of the doped conductive layer 150 is in a range of 1%to 20%, and optionally, a ratio of a sum of orthographic projectionareas of the plurality of first heavily doped regions 151 on thesubstrate 100 to a orthographic projection area of the doped conductivelayer 150 on the substrate 100 is in a range of 1% to 20%, inparticular, 5%, 3%, 10%, 15%, or 20%. The ratio in such a range canensure that the areas of the first heavily doped regions 151 are smallenough to avoid excessive optical absorption of the solar cell and thusfacilitate improvement of the photoelectric conversion efficiency of thesolar cell, and meanwhile, the areas of the first heavily doped regions151 are large enough to avoid a large sheet resistance of the firstheavily doped regions 151 and a small contact area with the electrodes170, which is conducive to reducing a contact resistance between thedoped conductive layer 150 and the electrodes 170, thereby improving thecurrent conductivity and the photoelectric conversion efficiency of thesolar cell.

In some embodiments, top surfaces of the first heavily doped regions 151facing away from the substrate 100 are flush with top surfaces of theother regions of the doped conductive layer 150. In other embodiments,the top surfaces of the first heavily doped regions 151 facing away fromthe substrate 100 is lower than the top surfaces of the other regions ofthe doped conductive layer 150 by less than 20% of the thickness of theother regions of the doped conductive layer 150.

In some embodiments, each of the first heavily doped regions 151 has awidth in a range of 20 μm to 100 μm in a direction along which theplurality of first heavily doped regions 151 are distributed,particularly, 20 μm, 40 μm, 58 μm, 82 μm or 100 μm. The plurality offirst heavily doped regions 151 are spaced apart from each other with adistance in a range of 0.8 mm to 4 mm in a direction along which theplurality of first heavily doped regions 151 are distributed,particularly, 0.8 mm, 1.5 mm, 2.8 mm, 3.6 mm or 4 mm. The widths of thefirst heavily doped regions 151 and the spaced distances between thefirst heavily doped regions 151 may further define the ratio of the sumof orthographic projection areas of the plurality of first heavily dopedregions 151 on the substrate 100 to the orthographic projection area ofthe doped conductive layer 150 on the substrate 100 being in a range of1% to 20%.

In some embodiments, the first heavily doped regions 151 located belowdifferent electrodes 170 are disposed at equal intervals such that thefirst heavily doped regions 151 can uniformly collect current.Optionally, the first heavily doped regions 151 located below a sameelectrode 170 are disposed at equal intervals so that the first heavilydoped regions 151 can uniformly collect current.

In some embodiments, the doping concentration of the plurality of firstheavily doped regions is in a range of 2E+20 cm⁻³ to 1E+22 cm⁻³. Thedoping ion concentration of the other regions of the doped conductivelayer 150 is in a range of 1E+20 cm⁻³ to 2E+20 cm⁻³, and the doping ionconcentration of the first heavily doped regions 151 is in a range of2E+20 cm⁻³ to 2E+21 cm⁻³.

It can be understood that the doping elements refer to a certain numberand a certain kind of impurities or elements doped into the crystal(s),including electrically active elements and non-electrically activeelements, whose concentration is roughly expressed as the “dopingconcentration.” The doping ion concentration in the embodiments of thepresent disclosure refers to a concentration of electrically activeimpurities (in ionized state). In this regard, the doping concentrationis greater than the doping ion concentration.

Further referring to FIG. 2 , in some embodiments, the depth of thefirst heavily doped region 151 is smaller than or equal to the thicknessof the doped conductive layer 150 in a direction perpendicular to thesurface 102 of the substrate 100.

In some embodiments, a ratio of the depth of the plurality of firstheavily doped regions 151 to the thickness of the doped conductive layer150 is in a range of 50% to 100%, particularly, 80% to 100%, and furtherparticularly, 80%, 88%, 92% or 100%.

It should be noted that the above description of the embodiments withrespect to FIG. 2 takes as an example that the first heavily dopedregions 151 do not extend through the doped conductive layer 150 alongits thickness. Alternatively, in other embodiments of the presentdisclosure, the first heavily doped regions 151 may be configured toextend through the doped conductive layer 150 along its thickness, thatis, the ratio of the depth of the plurality of first heavily dopedregions 151 to the thickness of the doped conductive layer 150 is 100%.Specifically, the following will be described in detail with referenceto FIG. 3 .

Referring to FIG. 3 , the substrate 100 has a plurality of secondheavily doped regions 103. A doping concentration in the plurality ofsecond heavily doped regions 103 is greater than a doping concentrationin other regions of the substrate 100 except the plurality of secondheavily doped regions 103. Each of the plurality of second heavily dopedregions 103 is aligned with a respective one of the plurality of firstheavily doped regions 151. The plurality of first heavily doped regions151 and the plurality of second heavily doped regions 103 have dopingelements of a same type.

The substrate 100 has the plurality of second heavily doped regions 103,and surfaces of the second heavily doped regions 103 are exposed fromthe substrate 100. The doping concentration in the second heavily dopedregions 103 is greater than the doping concentration in the otherregions of the substrate 100, which is conducive to improving transportefficiency for carriers, increasing open-circuit voltage, improvingcurrent transmission efficiency and thus the photoelectric conversionefficiency of the solar cell.

In some embodiments, the plurality of second heavily doped regions 103have a depth in a range of 0.001 μm to 1 μm in a direction perpendicularto the surface of the substrate 100, in particular 0.005 μm, 0.02 μm,0.09 μm, 0.4 μm or 0.9 μm. This can avoid tunneling effect caused by thehigh doping concentration in the second heavily doped regions 103, thatis, the doping element in the second heavily doped regions 103 does notdiffuse into a surface where the substrate 100 is in contact with theemitter 110 or into the emitter 110, so that the open-circuit voltage ofthe solar cell can be increased and the photoelectric conversionefficiency of the solar cell can be improved.

In some embodiments, in the direction along which the plurality of firstheavily doped regions 151 are distributed, the width of each of theplurality of first heavily doped regions 151 is smaller than a width ofa respective one of the plurality of second heavily doped regions 130.The doping concentration in the second heavily doped regions 103 isequal to the doping concentration in the first heavily doped regions151. The doping concentration in the second heavily doped regions 103 isin a range of 1E+20 cm⁻³ to 1E+22 cm⁻³, and the doping ion concentrationin the second heavily doped regions 103 is in a range of 1E+20 cm⁻³ to2E+20 cm⁻³. In other embodiments, the doping concentration in the secondheavily doped regions 103 is less than the doping concentration in thefirst heavily doped regions 151.

In some embodiments, the tunneling dielectric layer 140 has a pluralityof third heavily doped regions 141 extending through the tunnelingdielectric layer 140 along its thickness to contact the plurality offirst heavily doped regions 151 and the plurality of second heavilydoped regions 103, respectively. Each of the plurality of third heavilydoped regions 141 is aligned with a respective one of the plurality offirst heavily doped regions 151 and a respective one of the plurality ofsecond heavily doped regions 103. The plurality of first heavily dopedregions 151, the plurality of second heavily doped regions 103 and theplurality of third heavily doped regions 141 have doping elements of asame type. In this way, recombination loss between the tunnelingdielectric layer 140 and the substrate 100, and between the tunnelingdielectric layer 140 and the doped conductive layer 150 can be reduced,which is conducive to improving transport efficiency for carriers,increasing open-circuit voltage, improving current transmissionefficiency and thus the photoelectric conversion efficiency of the solarcell. Specifically, each third heavily doped region 141 has one endcontacting a respective first heavily doped region 151, and one otherend contacting a respective second heavily doped region 103.

In some embodiments, in the direction along which the plurality of firstheavily doped regions 151 are distributed, each second heavily dopedregion 103 has a width smaller than a width of a respective thirdheavily doped region 141, and each first heavily doped region 151 has awidth equal to the width of a respective third heavily doped region 141.In other embodiments, the width of each second heavily doped region 103is equal to a width of a respective third heavily doped region 141, andthe width of each first heavily doped region 151 is smaller than a widthof a respective third heavily doped region 141. In still otherembodiments, the width of each third heavily doped region 141 is largerthan the width of a respective first heavily doped region 151 and issmaller than the width of a respective second heavily doped region 103.In one example, the width of each first heavily doped region 151 is 50μm, the width of each third heavily doped region 141 is 60 μm, and thewidth of each second heavily doped region 103 is 70 μm.

In some embodiments, a doping concentration in the third heavily dopedregions 141 is in a range of 6E+19 cm⁻³ to 2E+20 cm⁻³. A doping ionconcentration in the third heavily doped regions 141 is in a range of6E+19 cm⁻³ to 1E+20 cm⁻³. The doping concentration in the third heavilydoped regions 141, the doping concentration in the second heavily dopedregions 103, and the doping concentration in the first heavily dopedregions 151 may be the same. In other embodiments, the dopingconcentration in the third heavily doped regions 141 is less than thedoping concentration in the first heavily doped regions 151, and is morethan the doping concentration in the second heavily doped regions 103.For example, the doping concentration in the first heavily doped regions151 is 4E+20 cm⁻³, the doping concentration in the third heavily dopedregions 141 is 3E+20 cm⁻³, and the doping concentration in the secondheavily doped regions 103 is 2E+20 cm⁻³.

It will be appreciated that the doping concentration in the firstheavily doped regions 151 may be evenly distributed, or may be increasedstepwise or gradually in a direction from the first heavily dopedregions 151 to the second heavily doped regions 103. The dopingconcentration of the second heavily doped regions 103 may be evenlydistributed, or may be decreased stepwise or gradually in a directionfrom the first heavily doped regions 151 to the second heavily dopedregions 103. The doping concentration of the third heavily doped regions141 may be evenly distributed, or may be decreased stepwise or graduallyin a direction from the first heavily doped regions 151 to the secondheavily doped regions 103.

It should be noted that the doping concentration in the first heavilydoped regions 151 of the doped conductive layer 150 of the solar cellshown in FIG. 2 may be the same or different from the dopingconcentration in the first heavily doped regions 151 of the dopedconductive layer 150 of the solar cell shown in FIG. 3 , and both are ina range of 2E+20 cm⁻³ to 1E+22 cm⁻³.

Similarly, the widths and the lengths of the first heavily doped regions151 and the spaced distances between the first heavily doped regions 151may be set according to different structural requirements, as long asthe ratio of the sum of the surface areas of the plurality of firstheavily doped regions 151 to the surface area of the doped conductivelayer 150 is in a range of 1% to 20%.

Further referring to FIGS. 1 to 3 , the passivation layer 160 may reducethe recombination of metal regions caused by the contact of theelectrodes 170 with the substrate 100, thereby improving efficiency ofthe cell. The passivation layer 160 may be of a single layer structureor a stacked layer structure, and may be made from a material includingat least one of silicon oxide, silicon nitride, silicon oxynitride,silicon oxycarbonitride, titanium oxide, hafnium oxide and aluminumoxide.

The electrodes 170 are grid lines of a solar cell for collecting andgathering current of the solar cell. The electrodes 170 may be formed bysintering a firing-through paste. The electrodes 170 may locally orfully contact the doped conductive layer 150. The electrodes 170 may bemade from a material including at least one of aluminum, silver, gold,nickel, molybdenum and copper. In some embodiments, the electrodes 170are bottom electrodes or back electrodes when the doped conductive layer150 is disposed on the rear surface of the substrate 100. In some cases,the electrodes 170 are fine grid lines or finger grid lines todistinguish from main grid lines or bus bars.

The first direction and the second direction may intersect so that atleast two first heavily doped regions 151 contact a same electrode 170,and an angle between the first direction and the second direction may bein a range of 0° to 90°, particularly, 90°, that is, the first heavilydoped regions 151 extend perpendicularly to the electrodes 170.

In some embodiments, further referring to FIG. 1 , the solar cellfurther includes a first passivation layer 120 disposed on a surface ofthe emitter 110 facing away from the substrate 100, the firstpassivation layer 120 being referred to as a front passivation layer,and a plurality of electrodes 130 spaced apart from each other andextending in the second direction, the plurality of electrodes 130penetrating the first passivation layer 120 to contact the emitter 110.

In some embodiments, the first passivation layer 120 may be of a singlelayer structure or a stacked layer structure, and the first passivationlayer 120 may be made from a material including at least one of siliconoxide, silicon nitride, silicon oxynitride, silicon oxycarbonitride,titanium oxide, hafnium oxide and aluminum oxide.

The electrodes 130 may be formed by sintering a firing-through paste.The electrodes 130 may locally or fully contact the emitter 110. Theelectrodes 170 may be made from a material including at least one ofaluminum, silver, nickel, gold, molybdenum and copper. In someembodiments, electrodes 130 are top electrodes or front electrodes. Insome cases, the electrodes 130 are fine grid lines or finger grid linesto distinguish from main grid lines or bus bars.

In the technical solutions of the solar cell provided in the embodimentsof the present disclosure, the doped conductive layer 150 has aplurality of first heavily doped regions 151 spaced apart from eachother and extending in a first direction, the doping concentration inthe plurality of first heavily doped regions 151 is greater than thedoping concentration in other regions of the doped conductive layer 150;the plurality of electrodes 170 are spaced apart from each other, and atleast two of the plurality of first heavily doped regions 151 are incontact with a same electrode 170. In this way, the doped conductivelayer 150 includes the first heavily doped regions 151 and the otherregions, that is, the doping concentration and the doping depth of thefirst heavily doped regions 151 can be appropriately set withoutaffecting the doping concentration and the thickness of the otherregions of the doped conductive layer 150. This is conducive to reducingsheet resistance and optical absorption of the doped conductive layer150, and improving photoelectric conversion efficiency of the solarcell. Since the doped conductive layer 150 has the plurality of firstheavily doped regions 151 spaced apart from each other and the dopingion concentration in the first heavily doped regions 151 is greater thanthe doping ion concentration in the other regions of the dopedconductive layer 150, the number of majority carriers in the firstheavily doped regions 151 is greater than that in the other regions,which improves capability of current transmission, and thus reduceseries resistance of the solar cell and improve the photoelectricconversion efficiency. Since at least two of the first heavily dopedregions 151 are in contact with the same electrode 170, a good ohmiccontact is formed between the first heavily doped regions 151 with thehigh doping concentration and the electrodes 170, and a contactresistance between the first heavily doped regions 151 with the highdoping concentration and the electrodes 170 is lower than that betweenthe other regions of the doped conductive layer 150 and the electrodes170, resulting in better current conduction effect and improvedphotoelectric conversion efficiency.

FIG. 5 is a schematic structural diagram of a solar cell according toanother embodiment of the present disclosure. The structure of the solarcell shown in FIG. 5 is partly the same as that of the solar cell shownin FIGS. 1 to 3 , with the main difference that the tunneling dielectriclayer and the doped conductive layer are disposed on the first surface(also referred to as the front surface) of the substrate. Details of thesame or similar contents or elements given in the embodiments withrespect to FIGS. 1 to 3 will not be repeated hereafter, and merelydetails for the difference will be described. The solar cell provided inanother embodiment of the present disclosure will be described in detailbelow with reference to FIG. 5 .

Referring to FIG. 5 , the solar cell includes a substrate 200, atunneling dielectric layer 240, a doped conductive layer 250, apassivation layer 260 and a plurality of electrodes 270. The substrate200 has a first surface 201 (also referred to as a front surface 201)and a second surface 202 (also referred to as a rear surface 202)opposing to each other. The tunneling dielectric layer 240 and the dopedconductive layer 250 are disposed on the first surface 201 of thesubstrate 200. The tunneling dielectric layer 240 is disposed betweenthe doped conductive layer 250 and the substrate 200. The passivationlayer 260 is disposed on a surface of the doped conductive layer 250facing away from the substrate 200, and the passivation layer 260 isreferred to as a front passivation layer. The plurality of electrodes270 (also referred to as first electrodes 270) are spaced apart fromeach other and extend in a second direction. Each electrode 270penetrates the passivation layer 260 to contact the doped conductivelayer 250. The solar cell further includes a second passivation layer207 disposed on the second surface 202 of the substrate 200 and aplurality of electrodes 208 (also referred to as second electrodes 208)penetrating the second passivation layer 207 to contact the substrate200. The second passivation layer 207 is referred to as a rearpassivation layer.

It will be appreciated that the solar cell shown in FIG. 5 may be aback-junction solar cell, i.e., a PN junction is formed on a rear sideof the cell. The doped conductive layer 250 and the substrate 200 havedoping elements of a same type. For example, the substrate 200 is anN-type substrate, and the doped conductive layer 250 is doped withN-type elements. For another example, the substrate 200 is a P-typesubstrate, and the doped conductive layer 250 is doped with P-typeelements. An emitter region is formed inside the substrate 200 near thesecond surface 202 and has a doping element of a type opposite to thatof the doping element in the substrate 200.

It will be appreciated that the doped conductive layer 250 is the sameas or similar to the doped conductive layer 150 described above withrespect to FIGS. 1 to 3 . That is, in other embodiments of the presentdisclosure, the doped conductive layer 250 may have a plurality of firstheavily doped regions spaced apart from each other. Similarly, thesubstrate 200 may have a plurality of second heavily doped regions, andthe tunneling dielectric layer 240 may have a plurality of third heavilydoped regions.

In some embodiments, the second passivation layer 207 may be of a singlelayer structure or a stacked layer structure. The second passivationlayer 207 may be made from a material including at least one of siliconoxide, silicon nitride, silicon oxynitride, silicon oxycarbonitride,titanium oxide, hafnium oxide and aluminum oxide.

The electrodes 208 may be formed by sintering a firing-through paste.The electrodes 208 may locally or fully contact the substrate 200. Theelectrodes 208 may be made from a material including at least one ofaluminum, silver, nickel, gold, molybdenum and copper.

In some embodiments, the electrodes 270 are top electrodes or frontelectrodes, and the electrodes 208 are bottom electrodes or backelectrodes.

For the solar cell shown in FIG. 5 , the tunneling dielectric layer 240and the doped conductive layer 250 are disposed on the first surface 201of the substrate 200, and the doped conductive layer 250 has theplurality of first heavily doped regions, thereby reducing sheetresistance and optical absorption of the doped conductive layer 250, andimproving photoelectric conversion efficiency of the solar cell.Meanwhile, the two first heavily doped regions contact the sameelectrode 270, so that a good ohmic contact can be formed, resulting inbetter current conduction effect and improved photoelectric conversionefficiency. In addition, the tunneling dielectric layer 240 and thedoped conductive layer 250 are disposed on the first surface 201 of thesubstrate 200, thereby reducing probability of recombination of thecarriers and holes on the first surface 201 of the substrate 200, andthe metal recombination caused by a direct contact between the electrode270 and the substrate 200, and thus improving the photoelectricconversion efficiency.

The foregoing solar cell discussed with respect to FIG. 1 or FIG. 5 isan example in which a tunneling dielectric layer and a doped conductivelayer having heavily doped regions are disposed on a single surface (afirst surface or a second surface) of a substrate. In other embodimentsof the present disclosure, it is further provided that each of the firstsurface and the second surface of the substrate is provided with thetunneling dielectric layer and the doped conductive layer disposedthereon, that is, the solar cell is a double-sided TOPCon cell. Detailsof the same or similar content or elements given in the embodiments ofFIGS. 1 to 5 will not be repeated hereafter, and merely details for thedifference will be described. The following will be described in detailwith reference to FIGS. 6 and 7 .

FIG. 6 is a schematic structural diagram of a solar cell according tostill another embodiment of the present disclosure. Referring to FIG. 6, a solar cell includes a substrate 300, a tunneling dielectric layer340 (also referred to as a first tunneling layer 340), a dopedconductive layer 350 (also referred to as a first conductive layer 350),a passivation layer 360 and a plurality of electrodes 370. The substrate300 has a first surface 301 and a second surface 302 opposing to eachother. The tunneling dielectric layer 340 and the doped conductive layer350 are disposed on the first surface 301 of the substrate 300. Thetunneling dielectric layer 340 is disposed between the doped conductivelayer 350 and the substrate 300. The passivation layer 360 is disposedon a surface of the doped conductive layer 350 facing away from thesubstrate 300, and the passivation layer 360 is referred to as a frontpassivation layer. The plurality of spaced electrodes 370 are spacedapart from each other and extend in a second direction. Each electrode370 penetrates the passivation layer 360 to contact the doped conductivelayer 350. The electrodes 370 are top electrodes or front electrodes.The solar cell further includes, stacked on the second surface 302 ofthe substrate 300 in sequence, a first tunneling dielectric layer 381, afirst doped conductive layer 382, a third passivation layer 383, and aplurality of electrodes 384. The electrodes 384 penetrate the thirdpassivation layer 383 to contact the first doped conductive layer 382.The third passivation layer 383 is referred to as a rear passivationlayer, and the electrodes 384 are bottom electrodes or back electrodes.

In some embodiments, the doped conductive layer 350 and the substrate300 have doping elements of a same type, and the first doped conductivelayer 382 has a doping element of a type opposite to that of the dopingelement in the substrate 300. In one example, the substrate 300 has anN-type doping element, the doped conductive layer 350 has an N-typedoping element, and the first doped conductive layer 382 has a P-typedoping element. In another example, the substrate 300 has a P-typedoping element, the doped conductive layer 350 has a P-type dopingelement, and the first doped conductive layer 382 has an N-type dopingelement.

It will be appreciated that the solar cell shown in FIG. 6 may be aback-junction solar cell.

The doped conductive layer 350 is the same as or similar to the dopedconductive layer 150 described above with respect to FIGS. 1 to 3 . Thatis, the doped conductive layer 350 may have a plurality of first heavilydoped regions spaced apart from each other. Similarly, the substrate 300may have a plurality of second heavily doped regions, and the tunnelingdielectric layer 340 may have a plurality of third heavily dopedregions.

In some embodiments, the first tunneling dielectric layer 381 may bemade from a material including any one of silicon oxide, siliconnitride, silicon oxynitride, intrinsic amorphous silicon and intrinsicpolysilicon. The first tunneling dielectric layer 381 may have athickness in a range of 0.5 nm to 2 nm, particularly, 0.5 nm to 1.5 nm,and further particularly, 0.5 nm to 1.2 nm. The first doped conductivelayer 382 may be made from a material including at least one ofpolysilicon, amorphous silicon and microcrystalline silicon. The firstdoped conductive layer 382 has a thickness in a range of 40 nm to 150nm, and particularly, 60 nm to 90 nm.

In some embodiments, the third passivation layer 383 may be of a singlelayer structure or a stacked layer structure. The third passivationlayer 383 may be made from a material including at least one of siliconnitride, silicon oxynitride, silicon oxycarbonitride, titanium oxide,hafnium oxide, and aluminum oxide.

The electrodes 384 may be formed by sintering a firing-through paste.The electrodes 384 may locally or fully contact the first dopedconductive layer 381. The electrodes 384 may be made from a materialincluding at least one of aluminum, silver, nickel, gold, molybdenum andcopper.

For the solar cell shown in FIG. 6 , the tunneling dielectric layer 340and the doped conductive layer 350 are disposed on the first surface 301of the substrate 300, thereby reducing probability of recombination ofthe carriers and holes on the first surface 301 of the substrate 300,and the metal recombination caused by a direct contact between theelectrode 370 and the substrate 300, and thus improving thephotoelectric conversion efficiency. The doped conductive layer 350 hasthe plurality of first heavily doped regions, thereby reducing sheetresistance and optical absorption of the doped conductive layer 350, andimproving photoelectric conversion efficiency of the solar cell.Meanwhile, the two first heavily doped regions contact the sameelectrode 370, so that a good ohmic contact can be formed, resulting inbetter current conduction effect and improved photoelectric conversionefficiency. Further, the first tunneling dielectric layer 381, the firstdoped conductive layer 382, the third passivation layer 383, and theelectrodes 384 are stacked on the second surface 302 of the substrate300 in sequence, and the electrodes 384 penetrate the third passivationlayer 383 to contact the first doped conductive layer 382. That is, thesolar cell is a double-sided TOPcon cell with both the first surface 301and the second surface 302 of the substrate 300 being light receivingsurfaces, which increases the surface area for collecting photogeneratedcarriers and thus improves the photoelectric conversion efficiency ofthe solar cell.

FIG. 7 is a schematic structural diagram of a solar cell according tostill another embodiment of the present disclosure. The structure of thesolar cell shown in FIG. 7 is partly the same as that of the solar cellshown in FIG. 6 . Details of the same or similar contents or elementsgiven in the above embodiments will not be repeated hereafter, andmerely details for the difference will be described.

Referring to FIG. 7 , a solar cell includes a substrate 400 having afirst surface 401 and a second surface 402 opposing to each other. Thesolar cell further includes, stacked on the first surface 401 of thesubstrate 400 in sequence, a first tunneling dielectric layer 481, afirst doped conductive layer 482, a third passivation layer 483, and aplurality of electrodes 484. The electrodes 484 penetrate the thirdpassivation layer 483 to contact the first doped conductive layer 482.The third passivation layer 483 is referred to as a front passivationlayer, and the electrodes 484 are top electrodes or front electrodes.The solar cell further includes a tunneling dielectric layer 440 (alsoreferred to as a second tunneling layer 440), a doped conductive layer450 (also referred to as a second conductive layer 450), a passivationlayer 460 and a plurality of electrodes 470. The tunneling dielectriclayer 440 and the doped conductive layer 450 are disposed on the secondsurface 402 of the substrate 400. The tunneling dielectric layer 440 isdisposed between the doped conductive layer 450 and the substrate 400.The passivation layer 460 is disposed on a surface of the dopedconductive layer 450 facing away from the substrate 400, and thepassivation layer 460 is referred to as a rear passivation layer. Theplurality of spaced electrodes 470 are spaced apart from each other andextend in a second direction. Each electrode 470 penetrates thepassivation layer 460 to contact the doped conductive layer 450. Theelectrodes 470 are bottom electrodes or back electrodes.

The doped conductive layer 450 is the same as or similar to the dopedconductive layer 150 described above with respect to FIGS. 1 to 3 . Thatis, the doped conductive layer 450 may have a plurality of first heavilydoped regions spaced apart from each other. Similarly, the substrate 400may have a plurality of second heavily doped regions, and the tunnelingdielectric layer 440 may have a plurality of third heavily dopedregions.

In some embodiments, the doped conductive layer 450 and the substrate400 have doping elements of a same type, and the first doped conductivelayer 482 has a doping element of a type opposite to that of the dopingelement in the substrate 400. In one example, the substrate 400 has anN-type doping element, the doped conductive layer 450 has an N-typedoping element, and the first doped conductive layer 482 has a P-typedoping element. In another example, the substrate 400 has a P-typedoping element, the doped conductive layer 450 has a P-type dopingelement, and the first doped conductive layer 482 has an N-type dopingelement.

It will be appreciated that the solar cell shown in FIG. 7 may be afront-junction solar cell.

Accordingly, in another aspect, the embodiments of the presentdisclosure further provide a photovoltaic module for converting receivedlight energy into electrical energy. The photovoltaic module includes acell string, a package adhesive film and a cover plate. The cell stringincludes a plurality of solar cells. The package adhesive film isconfigured to cover a surface of the cell string. The cover plate isconfigured to cover a surface of the package adhesive film facing awayfrom the cell string. The solar cells are any of the solar cells in theabove embodiments described with respect to FIGS. 1 to 7 .

The package adhesive film be an organic package adhesive film, such asan ethylene-vinyl acetate copolymer (EVA) adhesive film, or apolyethylene octene co-elastomer (POE) adhesive film. The packageadhesive film covers a surface of the cell string for sealing. The coverplate may be a glass cover plate or a plastic cover plate configured tocover a surface of the package adhesive film facing away from the cellstring. In some embodiments, a light trapping structure is provided onthe cover plate to improve utilization of incident light. Thephotovoltaic module has a higher ability in current collection and alower rate in carrier recombination, thereby improving photoelectricconversion efficiency.

Accordingly, in yet another aspect, the embodiments of the presentdisclosure provide a method for manufacturing the solar cell provided inthe foregoing embodiments with respect to FIGS. 1 to 7 . Details of thesame or similar contents or elements given in the above embodiments willnot be repeated hereafter, and merely details for the difference will bedescribed. As an example, the embodiments of the present disclosureprovides a method for manufacturing the solar cell as shown in FIGS. 1to 3 .

Referring to FIGS. 4 and 8 to 16 , FIGS. 8 to 16 are schematicstructural diagrams corresponding to various steps of a method formanufacturing a solar cell according to an embodiment of the presentdisclosure. Specifically, FIGS. 11 to 14 show merely a local structure,i.e., the structure on the second surface of the substrate of the solarcell.

Referring to FIG. 8 , a substrate 100 is provided and has a firstsurface 101 and a second surface 102 opposing to each other.

Referring to FIG. 9 , an emitter 110 is formed on the first surface 101of the substrate 100.

Referring to FIGS. 10 to 13 , the tunneling dielectric layer 140 and thedoped conductive layer 150 are formed. The doped conductive layer 150 isdisposed on the second surface 102 of the substrate 100, and thetunneling dielectric layer 140 is disposed between the doped conductivelayer 150 and the substrate 100. The doped conductive layer 150 has aplurality of first heavily doped regions 151 spaced apart from eachother and extending in a first direction. The first heavily dopedregions 151 are exposed from a surface of the doped conductive layer 150facing away from the substrate 100. A doping concentration in the firstheavily doped regions 151 is greater than a doping concentration inother regions of the doped conductive layer 150.

In some embodiments, the tunneling dielectric layer 140 is formed by atleast one of a Low Pressure Chemical Vapor Deposition (LPCVD) method anda Plasma Enhanced Chemical Vapor Deposition (PECVD) method.

The steps of forming the doped conductive layer 150 will be described indetail below with reference to FIGS. 11 to 14 .

Referring to FIG. 11 , an initial doped conductive layer 104 is formedon a surface of the tunneling dielectric layer 140 facing away from thesubstrate 100 and has a doping element therein.

In some embodiments, the initial doped conductive layer 104 may beformed by performing diffusion or ion implantation on an intrinsic dopedconductive layer which is formed by the LPCVD method. The intrinsicdoped conductive layer may be an intrinsic polysilicon layer. In otherembodiments, the initial doped conductive layer 104 is formed byannealing an initial doped conductive film which may be formed by thePECVD method. The initial conductive film may be made from a materialincluding amorphous silicon or microcrystalline silicon. The initialdoped conductive layer 104 may include at least one of a polysiliconlayer, an amorphous silicon layer, and a microcrystalline silicon layer.For example, the initial doped conductive layer 104 in the presentdisclosure includes a polysilicon layer.

In some embodiments, the relationship between the doping concentrationand the doping depth of the initial doped conductive layer 104 conformsto the curves shown in the ECV doping graph of FIG. 4 . The curvesinclude a curve for the first heavily doped regions and a curve for theother regions of the initial doped conductive layer 104. The specificdoping concentration and the specific doping depth of the initial dopedconductive layer 104 are not limited herein, as long as the curves shownin FIG. 4 are satisfied.

In some embodiments, the initial doped conductive layer 104 and thesubstrate 100 may have doping elements of a same type. For example, thedoping element in the substrate 100 is of the N type, and the dopingelement in the initial doped conductive layer 104 is of the N type.

In some embodiments, the initial doped conductive layer 104 has athickness in a range of 40 nm to 150 nm, and particularly, 60 nm to 90nm. This can ensure lower optical loss of a doped conductive layerformed subsequently and good interface passivation effect of thetunneling dielectric layer 140, thereby improving efficiency of thecell. The initial doped conductive layer 104 may have the thickness, butis not limited to, in a range of 40 nm to 150 nm, or may be otherthicknesses known to those skilled in the art.

Referring to FIGS. 11 and 12 , a doping process is performed on localregions of the initial doped conductive layer 104 for increasing theconcentration of doping element in the local regions to form firstheavily doped regions 151. In this way, a doped conductive layer 150 isformed.

It can be understood that the doping elements in the doping processrefer to a certain number and a certain kind of impurities or elementsdoped into the crystal(s), including electrically active elements andnon-electrically active elements, whose concentration is roughlyexpressed as the “doping concentration.” The doping ion concentration inthe embodiments of the present disclosure refers to a concentration ofelectrically active impurities (in ionized state). In this regard, thedoping concentration is greater than the doping ion concentration.

Specifically, referring to FIG. 11 , a doping source layer 105 havingdoping elements therein is formed on a surface of the initial dopedconductive layer 104.

In some embodiments, the doping source layer 105 covers entirely thesurface of the initial doped conductive layer 104. The doping sourcelayer 105 may be made from a material including, but is not limited to,phosphosilicate glass (PSG) or borophosphosilicate glass (BPSG).

Referring to FIG. 12 , a diffusion process is performed to diffusedoping ions in local regions of the doping source layer 105 (refer toFIG. 10 ) into the initial doped conductive layer 104 to form the firstheavily doped regions 151. The doping source layer 105 is then removed.

In some embodiments, the diffusion process is performed locally by usinga laser process. The doping source layer 105 is completely removed bywet etching, so as to prevent the silicon wafer from getting damped inthe air caused by residual phosphor-silicate glass to lower the currentand power. It is also possible to prevent the passivation layersubsequently formed in the doped conductive layer 150 from detachingtherefrom, thereby improving the photoelectric conversion efficiency ofthe solar cell. The solution for the wet etching is a mixture liquid ofHNO3 and HF. In other embodiments, the diffusion process may beperformed using a thermal diffusion process or an ion implantationprocess.

It should be noted that the foregoing description with respect to FIGS.11 and 12 is an example in which the doping source layer 105 coversentirely the surface of the initial doped conductive layer 104. In otherembodiments of the present disclosure, a plurality of doping sourcesub-layers spaced apart from each other may be formed. Specifically, thefollowing will be described in detail with reference to FIG. 13 .

Referring to FIG. 13 , a plurality of doping source sub-layers 106 areformed on the surface of the initial doped conductive layer 104. Thedoping source sub-layers 106 are spaced apart from each other and extendin a first direction.

In some embodiments, a ratio of a sum of surface areas of the dopingsource sub-layers 106 to a surface area of the initial doped conductivelayer 104 is in a range of 1% to 20%. Specifically, a ratio of a sum oforthographic projection areas of the doping source sub-layers 106 on thesubstrate 100 to an orthographic projection area of the initial dopedconductive layer 106 on the substrate 100 is in a range of 1% to 20%,and particularly, 5%, 3%, 10%, 15%, or 20%. The ratio in such a rangecan ensure that the areas of the first heavily doped regions formedsubsequently are small enough to avoid excessive optical absorption ofthe solar cell and thus facilitate improvement of the photoelectricconversion efficiency of the solar cell, and meanwhile, the areas of thefirst heavily doped regions are large enough to avoid a large sheetresistance of the first heavily doped regions and a small contact areawith electrodes formed subsequently, which is conducive to reducing acontact resistance between the doped conductive layer and theelectrodes, thereby improving the current conductivity and thephotoelectric conversion efficiency of the solar cell.

In some embodiments, the doping source sub-layers 106 located belowdifferent electrodes formed subsequently are disposed at equal intervalssuch that the first heavily doped regions formed subsequently canuniformly collect current. Optionally, the doping source sub-layers 106located below a same electrode formed subsequently are disposed at equalintervals so that the first heavily doped regions formed subsequentlycan uniformly collect current.

In some embodiments, each of the doping source sub-layers 106 has awidth in a range of 20 μm to 100 μm in a direction along which theplurality of doping source sub-layers 106 are distributed, particularly,20 μm, 40 μm, 58 μm, 82 μm or 100 μm. The plurality of doping sourcesub-layers 106 are spaced apart from each other with a distance in arange of 0.8 mm to 4 mm in a direction along which the plurality ofdoping source sub-layers 106 are distributed, particularly, 0.8 mm, 1.5mm, 2.8 mm, 3.6 mm or 4 mm. The widths of the doping source sub-layers106 and the spaced distances between the doping source sub-layers 106may further define the ratio of the sum of surface areas of the firstheavily doped regions formed subsequently to the surface area of thedoped conductive layer being in a range of 1% to 20%.

In some embodiments, the doping source sub-layers 106 may be made from amaterial including, but is not limited to, phosphosilicate glass orborophosphosilicate glass.

Further referring to FIG. 12 , a diffusion process is performed todiffuse doping ions in the doping source sub-layers 106 (refer to FIG.13 ) into the initial doped conductive layer 104 to form the firstheavily doped regions 151. The doping source sub-layers 106 are thenremoved.

It will be understood that the doping process may cause the top surfacethe initial doped conductive layer 104 facing away from the substrate100 to be etched to a certain extent, that is, the top surfaces of thefirst heavily doped regions 151 facing away from the substrate 100 islower than those of the other regions of the doped conductive layer 150by less than 20% of the thickness of the other regions of the dopedconductive layer 150. Alternatively, the top surfaces of the firstheavily doped regions 151 facing away from the substrate 100 is flushwith the top surfaces of the other regions of the doped conductive layer150.

In other embodiments, referring to FIG. 14 , a diffusion process isperformed to diffuse doping elements in local regions of the dopingsource layer 105 (refer to FIG. 11 ) into the initial doped conductivelayer 104 to form the first heavily doped regions 151, and the dopingelements are further diffused into the tunneling dielectric layer 140 toform third heavily doped regions 141 each aligned with a respectivefirst heavily doped region 151, and into the substrate 100 of a certainthickness to form second heavily doped regions 103 each aligned with arespective first heavily doped region 151 and. The doping source layer105 is the removed.

In some embodiments, the first heavily doped regions 151 extend throughthe doped conductive layer 150 along its thickness, that is, the ratioof the depth of the first heavily doped regions 151 to the thickness ofthe doped conductive layer 150 is 100%.

It should be noted that the doping concentration of the first heavilydoped regions 151 of the solar cell shown in FIG. 12 may be the same asor different from the doping concentration of the first heavily dopedregions 151 of the solar cell shown in FIG. 14 , and both are in a rangeof 2E+20 cm⁻³ to 1E+22 cm⁻³.

Similarly, the widths and lengths of the first heavily doped regions 151and the distances between the first heavily doped regions 151 may be setaccording to different structural requirements, as long as the ratio ofthe sum of the surface areas of the plurality of first heavily dopedregions 151 to the surface area of the doped conductive layer 150 is ina range of 1% to 20%.

The solar cells of FIGS. 12 and 14 may be formed using a nanosecondlaser with a laser wavelength of 532 nm or other laser that can achievedoping, and the process parameters of the diffusion process for formingthe solar cells of FIGS. 12 and 14 may be different. In someembodiments, the process parameters for forming the solar cell shown inFIG. 12 include a laser power of 5 W to 40 W and a laser frequency of 50KHz to 250 KHz. The process parameters for forming the solar cell shownin FIG. 14 include a laser power of 40 W to 100 W and a laser frequencyof 250 KHz to 450 KHz.

Referring to FIG. 15 , a passivation layer 160 is formed on a surface ofthe doped conductive layer 150 facing away from the substrate 100.

Further referring to FIG. 15 , a first passivation layer 120 is formedon a surface of the emitter 110 facing away from the substrate 100.

Referring to FIG. 16 , a plurality of electrodes 170 are formed. Theelectrodes 170 are spaced apart from each other and extend in a seconddirection. Each of the electrodes 170 penetrates the passivation layer160 to contact the doped conductive layer 150, and at least two firstheavily doped regions 151 are in contact with a same electrode 170.

Further referring to FIG. 18 , a plurality of electrodes 130 are formed.The electrodes 130 are spaced apart from each other and extend in asecond direction. Each of the electrodes 130 penetrates the firstpassivation layer 120 to contact the emitter 110.

In other embodiments, a method for manufacturing a solar cell isprovided to form a solar cell as shown in FIG. 5 . The method includes:providing a substrate 200 having a first surface 201 and a secondsurface 202 opposing to each other; forming, sequentially stacked on thefirst surface 201, a tunneling dielectric layer 240, a doped conductivelayer 250, a passivation layer 260 and a plurality of electrodes 270,the plurality of electrodes 270 being spaced apart from each other andpenetrating the passivation layer 260 to contact the doped conductivelayer 250; forming, sequentially stacked on the second surface 202, asecond passivation layer 207 and a plurality of electrodes 208, theplurality of electrodes 208 penetrating the second passivation layer 207to contact the substrate 200.

It will be understood that the process step of forming the secondpassivation layer 207 is the same as or similar to the process step offorming the first passivation layer 120 (as shown in FIG. 15 ) in theabove-described embodiments, and details thereof will not be describedhereafter. Similarly, the process step of forming the electrodes 208 isthe same as or similar to the process step of forming the electrodes 130(as shown in FIG. 16 ) of the above-described embodiments.

In still other embodiments, a method for manufacturing a solar cell isprovided to form a solar cell as shown in FIG. 6 . The method includes:providing a substrate 300 having a first surface 301 and a secondsurface 302 opposing to each other; forming, sequentially stacked on thefirst surface 301, a tunneling dielectric layer 340, a doped conductivelayer 350, a passivation layer 360, and a plurality of electrodes 370,the plurality of electrodes 370 being spaced apart from each other andpenetrating the passivation layer 360 to contact the doped conductivelayer 350; forming, sequentially stacked on the second surface 302, afirst tunneling dielectric layer 381, a first doped conductive layer382, a third passivation layer 383 and a plurality of electrodes 384,the plurality of electrodes 384 penetrating the third passivation layer383 to contact the first doped conductive layer 382.

It will be understood that the process step of forming the firsttunneling dielectric layer 381 is the same as or similar to the processstep of forming the tunneling dielectric layer 140 (as shown in FIG. 10) in the above-described embodiments, and details thereof will not bedescribed hereafter. Similarly, the process step of forming the firstdoped conductive layer 382 is the same as or similar to the process stepof forming the doped conductive layer 150 (as shown in FIG. 10 ) of theabove-described embodiments. The process step of forming the thirdpassivation layer 383 is the same as or similar to the process step offorming the passivation layer 160 (as shown in FIG. 15 ) of theabove-described embodiments. The process step of forming the electrodes384 is the same as or similar to the process step of forming theelectrodes 170 (as shown in FIG. 15 ) of the above-describedembodiments.

In still other embodiments, a method for manufacturing a solar cell isprovided to form a solar cell as shown in FIG. 7 . The method includes:providing a substrate 400 having a first surface 401 and a secondsurface 402 opposing to each other; forming, sequentially stacked on thefirst surface 401, a first tunneling dielectric layer 481, a first dopedconductive layer 482, a third passivation layer 483, and a plurality ofelectrodes 484, the plurality of electrodes 484 penetrating the thirdpassivation layer 483 to contact the first doped conductive layer 482;forming, sequentially stacked on the second surface 402, a tunnelingdielectric layer 440, a doped conductive layer 450, a passivation layer460, and a plurality of electrodes 470, the plurality of electrodes 470being spaced apart from each other and penetrating the passivation layer460 to contact the doped conductive layer 450.

Those skilled in the art should appreciate that the aforementionedembodiments are specific embodiments for implementing the presentdisclosure. In practice, however, various changes may be made in theforms and details of the specific embodiments without departing from thespirit and scope of the present disclosure. Any person skilled in theart may make their own changes and modifications without departing fromthe spirit and scope of the present disclosure, so the protection scopeof the present disclosure shall be subject to the scope defined by theclaims.

1. A solar cell, comprising: a substrate; a tunneling dielectric layerand a doped conductive layer disposed on the substrate, wherein thetunneling dielectric layer is disposed between the doped conductivelayer and a surface of the substrate, the doped conductive layer has adoping element of an N type or a P type, the doped conductive layer hasa plurality of first heavily doped regions spaced apart from each otherand extending in a first direction, and a doping concentration in theplurality of first heavily doped regions is greater than a dopingconcentration in other regions of the doped conductive layer, whereinthe doping concentration in each of the plurality of first heavily dopedregions decreases gradually in a direction from the doped conductivelayer to the substrate; a passivation layer disposed on a surface of thedoped conductive layer facing away from the substrate; and a pluralityof electrodes spaced apart from each other and extending in a seconddirection, wherein the plurality of electrodes penetrate the passivationlayer to contact the doped conductive layer, and at least two of theplurality of first heavily doped regions are in contact with a sameelectrode; wherein the substrate has a plurality of second heavily dopedregions, a doping concentration in the plurality of second heavily dopedregions is greater than a doping concentration in other regions of thesubstrate, each of the plurality of second heavily doped regions isaligned with a respective one of the plurality of first heavily dopedregions, and the plurality of first heavily doped regions and theplurality of second heavily doped regions have doping elements of a sametype.
 2. (canceled)
 3. (canceled)
 4. The solar cell according to claim1, wherein a thickness of the doped conductive layer is in a range of 40nm to 150 nm.
 5. (canceled)
 6. The solar cell according to claim 1,wherein the doping concentration in the plurality of second heavilydoped regions is less than or equal to the doping concentration in theplurality of first heavily doped regions, and the doping concentrationin each of the plurality of second heavily doped regions decreasesgradually in the direction from the doped conductive layer to thesubstrate.
 7. The solar cell according to claim 1, wherein the dopingconcentration in the plurality of first heavily doped regions is in arange of 2E+20 cm-3 to 1E+22 cm-3.
 8. The solar cell according to claim1, wherein the plurality of second heavily doped regions each have adepth in a range of 0.001 μm to 1 μm in a direction perpendicular to thesurface of the substrate.
 9. The solar cell according to claim 1,wherein the tunneling dielectric layer has a plurality of third heavilydoped regions extending through the tunneling dielectric layer along athickness direction thereof to contact the plurality of first heavilydoped regions and the plurality of second heavily doped regions,respectively, each of the plurality of third heavily doped regions isaligned with a respective one of the plurality of first heavily dopedregions, and the plurality of first heavily doped regions and theplurality of third heavily doped regions have doping elements of a sametype.
 10. The solar cell according to claim 9, wherein in a directionalong which the plurality of first heavily doped regions aredistributed, each of the plurality of first heavily doped regions has awidth less than a width of a respective one of the plurality of secondheavily doped regions, and smaller than or equal to a width of arespective one of the plurality of third heavily doped regions.
 11. Thesolar cell according to claim 1, wherein a ratio of a sum of surfaceareas of the plurality of first heavily doped regions to a surface areaof the doped conductive layer is in a range of 1% to 20%.
 12. The solarcell according to claim 1, wherein each of the plurality of firstheavily doped regions has a width in a range of 20 μm to 100 μm in adirection along which the plurality of first heavily doped regions aredistributed.
 13. The solar cell according to claim 1, wherein theplurality of first heavily doped regions are spaced apart from eachother with a distance in a range of 0.8 mm to 4 mm in a direction alongwhich the plurality of first heavily doped regions are distributed. 14.The solar cell according to claim 1, wherein the doped conductive layerincludes at least one of a polysilicon layer, an amorphous siliconlayer, and a microcrystalline silicon layer.
 15. The solar cellaccording to claim 1, wherein the substrate has a first surface and asecond surface opposing to each other, and the tunneling dielectriclayer and the doped conductive layer are disposed on at least one of thefirst surface and the second surface of the substrate.
 16. The solarcell according to claim 1, wherein the substrate and the dopedconductive layer have doping elements of a same type.
 17. A photovoltaicmodule, comprising: a cell string including a plurality of solar cells;a package adhesive film configured to cover a surface of the cellstring; a cover plate configured to cover a surface of the packageadhesive film facing away from the cell string; wherein each solar cellof the plurality of solar cells in the cell string includes: asubstrate; a tunneling dielectric layer and a doped conductive layerdisposed on the substrate, wherein the tunneling dielectric layer isdisposed between the doped conductive layer and a surface of thesubstrate, the doped conductive layer has a doping element of an N typeor a P type, the doped conductive layer has a plurality of first heavilydoped regions spaced apart from each other and extending in a firstdirection, and a doping concentration in the plurality of first heavilydoped regions is greater than a doping concentration in other regions ofthe doped conductive layer, wherein the doping concentration in each ofthe plurality of first heavily doped regions decreases gradually in adirection from the doped conductive layer to the substrate; apassivation layer disposed on a surface of the doped conductive layerfacing away from the substrate; and a plurality of electrodes spacedapart from each other and extending in a second direction, wherein theplurality of electrodes penetrate the passivation layer to contact thedoped conductive layer, and at least two of the plurality of firstheavily doped regions are in contact with a same electrode; wherein thesubstrate has a plurality of second heavily doped regions, a dopingconcentration in the plurality of second heavily doped regions isgreater than a doping concentration in other regions of the substrate,each of the plurality of second heavily doped regions is aligned with arespective one of the plurality of first heavily doped regions, and theplurality of first heavily doped regions and the plurality of secondheavily doped regions have doping elements of a same type. 18.(canceled)
 19. (canceled)
 20. The photovoltaic module according to claim17, wherein a thickness of the doped conductive layer is in a range of40 nm to 150 nm.